Human beings are the product of habits and
heritage. Before the advent of alarm clocks, many farmers woke up hearing the rooster
crowing, announcing the arrival of morning. They milked their cows, worked in the farm and
went into bed at night. There was no electricity. So, daylight announced the initiation
and termination of many activities.

Modern life style differs significantly
from these early days. Most of us wake up in the morning, not by hearing a rooster crow or
by feeling the golden rays of sunlight slowly drifting into our rooms; we wake up by the
alarm clock or by the clock radio. Many of us have tough time getting up at the first
time; so we set the "snooze" button to give us a little more of precious time to
sleep. The windows have heavy drapes, so most of us do not see the sunlight except when we
peek outside. In the evening, many of us stay awake to watch the late night shows. (Now we
have light night shows and late late night shows to keep us company till the wee hours of
the night.)

The problem is that our system needs time
to sleep. Studies on animals have shown that they have definite patterns they follow every
day depending on the season. In autumn, most of the plants and animals get ready to go
into "hibernation" for the winter period. Many birds migrate to south for the
winter. During this period, they do not eat much (There is not much food to be found.)
But, come spring, nature become very lively. The birds return from the south. The trees
starts the new growth.

Many animals are found to time the events
in their lives depending on the season, so that the functions can be accomplished at the
most effective way. For example, lambs are born only in the spring when there is plentiful
of food for the mother to nurse the newborn. Most of the animal species coordinate the
mating time so that the birth occurs in the season when there is plenty of food available.
In the tropical rainforests, birds wait till the dry season to breed. In Arctic, the
breeding is timed to coincide with the melting of snow and ice.

The question is how do animals know how to
predict the seasons in advance? Is it the temperature fluctuations? It cannot be, because,
sometimes we have the "so called Indian Summer" in fall; but the birds do fine.
It turns out that the most important factor is the day light; or more specifically the
day/night cycle. Animals and plants sense the shortening of the days in the fall and
perceive the arrival of winter. In spring, the lengthening of the day signifies the
arrival of spring and summer. Most of the expert horticulturists know about this. They
manipulate the "day light hours" (or photoperiod) to coax the poinsettia to
bloom in time for the Christmas season, daylilies to bloom for the Easter (although Easter
can be in March or April), etc.

It turns out that human beings are also
influenced by the light. Light determines our sleep/wake cycle. In most animals and
humans, the desire to sleep is brought on by secretion of a hormone called melatonin.
Melatonin is produced in a tiny gland known as the pineal gland. In the evening the pineal
gland reacts to the diminishing levels of daylight and starts to produce melatonin, which
is then released into the blood and flows through the body making us drowsy. Its secretion
peaks in the middle of the night during our heaviest hours of sleep. In the morning,
bright light shining through the eye reaches the pineal gland which reacts by switching
off the production of melatonin, thus removing the desire to sleep.

The pineal gland is linked up to the rest
of the hormonal system. Consequently melatonin production also influences the functioning
of other parts of the body. During darkness and sleep, melatonin modifies the secretion of
hormones from organs such as the pituitary, the master gland of the hormonal system. The
pituitary in turn regulates the secretion of hormones controlling growth, milk production,
egg and sperm production. It also regulates the action of the thyroid gland, which is
concerned with metabolism, and the adrenal glands, which control excretion of the body's
waste. It is obvious then that fluctuations in light and darkness according to the seasons
of the year will influence rhythms of growth, reproduction and activity in animals and
indeed humans.

Statistics show that despite living and
working in "closed structures", our bodies still respond to the external
environment and to its seasonal variability in duration and intensity. Scientist have
found that growth rates in children are affected by the seasons. For example, surveys
carried out in Germany, Sweden and Scotland show that height and weight increase is more
predominant in the spring and early summer. In many countries the rate of conception peaks
in the summer when the hours of daylight are longest. In numerous trials the seasons have
been seen to influence the timing and duration of sleep, pain threshold, alertness, eating
habits, mood, the onset of menstruation in women and sexual activity.